Generally, when a user uses a system provided with resources such as a server and a disk, these resources are normally occupied by the user. However, depending upon timing, though resources are once occupied, they are not used for a certain period, afterward, may be used again, and the resources are not necessarily ordinarily occupied. Therefore, when another user requests while the resources are not used, it is desirable that the use of the resources is permitted and the resources are efficiently distributed.
Recently, a new computer system called a private cloud attracts a great deal of attention. In the private cloud, information processing that exceeds the performance of resources of an individual computer is enabled by accessing to resources shared in the cloud. As a user can share the resources in the cloud, the whole resources of the computer system are efficiently utilized and its operational cost can be reduced.
Incidentally, for one technology for enhancing a utilization factor of resources, virtualization technology can be mentioned. According to the virtualization technology, various processing can be simultaneously executed as plural logical computers even in one physical computer by configuring a virtual computer inside a computer such as PC. Therefore, in a view from the whole system provided with such plural computers, the number of physical computers can be reduced, a utilization factor of resources of the whole system is enhanced, and the cost can be reduced (for example, refer to JP-A No. 2008-217302).